A METHOD AND A SYSTEM FOR ADJUSTING VELOCITY SET POINTS FOR REGULATING THE VELOCITY OF A VEHICLE
A method and a system for adjusting set points for regulating the velocity of a vehicle: The velocity regulation uses at least one cruise control and one downhill speed control. A cruise control controls an engine system with a velocity set point vref based on a selected set velocity vset. The downhill speed control controls a brake system with a braking set point vdhsc—ref based on a downhill speed control velocity vdhsc, wherein the downhill speed control velocity vdhsc is related to the set velocity vset by an offset voffset. The velocity set point vref and the braking set point vdhsc—ref are adjusted by at least one shift vshift, which has a value corresponding to the offset voffset, vshift=voffset, wherein the adjustment is performed based on an actual behavior of the vehicle. As high an actual average velocity as possible is achieved hereby.
The present invention concerns a method for adjusting the set points for regulating the velocity of a vehicle according to the preamble of claim 1, and a system for adjusting the set points for regulating the velocity of a vehicle according to the preamble of claim 15.
The present invention also concerns a computer program and a computer program product that implement the method according to the invention.
BACKGROUNDCruise control is currently commonly present in motor vehicles, such as cars, goods vehicles and buses. One purpose of cruise control is to achieve a uniform predetermined velocity. Cruise control is often realized in vehicles by two interworking systems; a cruise control system, which demands engine torque from an engine system, and a downhill speed control system, which prevents the vehicle from reaching too high a velocity, primarily on downhill stretches.
The cruise control thus adapts the engine torque to prevent retardation or alternatively applies braking action in the downhill stretches on which the vehicle accelerates because of its own weight. One overarching purpose of the cruise control is to achieve driving convenience and greater comfort for the driver of the motor vehicle, as the driver does not need to step on the accelerator in order for the vehicle to maintain a velocity set by the driver, i.e. a set velocity vset. The set velocity vset is the velocity that the driver wants the motor vehicle to maintain on flat road. The cruise control then provides an engine system in the vehicle with the set velocity user as a velocity set point vref for controlling the engine system. The set velocity vset is often related to a speed limit for a section of road on which the vehicle is present, e.g. the set velocity vset is often set by the driver to the value 89 km/h where the speed limit is 90 km/h.
The downhill speed control automatically brakes the vehicle when a downhill speed control (DHSC) velocity vdhsc is reached. The downhill speed control velocity vdhsc is thus used as a braking set point vdhsc
The downhill velocity control thus regulates the velocity of, for instance, heavy vehicles on downhill stretches, as such vehicles accelerate on downhill stretches due to their own weight. The regulation performed by the downhill speed control system utilizes auxiliary brakes, which can comprise, for instance, a retarder, and an exhaust brake or a four-stage electronic brake (Telma). Other types of brakes can also be utilized by the downhill speed control.
BRIEF DESCRIPTION OF THE INVENTIONBecause the known cruise control of the vehicle consists of two interworking systems; the cruise control system and the downhill speed control system, it is important that these systems actually interwork with one another and do not counteract one another. Typically a situation should be avoided in which the cruise control is demanding engine torque while the downhill speed control is simultaneously braking the vehicle, which would result in an uneconomical and uncomfortable forward travel of the vehicle. In addition, the regulation performed by each system would be negatively affected by its being counteracted by the other system, putting said regulation at risk of becoming unstable.
Relating, as noted above, the downhill speed control velocity vdhsc to the set velocity vset, e.g. vdhsc=vset+voffset, causes the offset velocity voffset to create a margin between the respective set points vdhsc
However, the set velocity vset set by the driver for the cruise control and thereby also, through its relation to the set velocity vset, the set downhill speed control velocity vdhsc, entails a non-optimized regulation of the velocity of the vehicle, primarily on hilly roads or road sections that comprise one or more uphill or downhill stretches. This is because the set velocity vset is usually set somewhat below the prevailing speed limit, e.g. the set velocity is often set to 89 km/h, vset=89 km/h, if the speed limit for the road is 90 km/h. This causes the downhill speed control velocity to be somewhat higher than said speed limit, e.g. vdhsc=92 km/h, because of the offset velocity.
Because the downhill speed control velocity here is somewhat higher than the 90 km/h speed limit, e.g. vdhsc=92 km/h, the vehicle will accelerate up to said downhill speed control velocity on relatively long downhill stretches and then remain at said velocity, vact=vdhsc=92 km/h, on the downhill stretch. This causes the vehicle, for a relatively long period of time, i.e. on a large part of the downhill stretches, to exceed the prevailing speed limit, which means that the driver will be at risk of being fined by the authorities for speeding, or be at risk of getting a speeding ticket, a so-called “demerit point” on their driver's license. Many vehicles are equipped with a tachograph, which can be at least partly electronic. A tachograph records the forward travel of the vehicle, and at its velocity. In some countries the authorities can demand to see tachograph cards, and also can fine the driver if the tachograph card indicates that a violation of the speed limit has been perpetrated.
One solution to this problem would be to lower the level of the set velocity vset, which would also lower the downhill speed control velocity vdhsc so that the speed limit would not be exceeded on downhill stretches. But then the vehicle would, on flat roads, maintain an actual vehicle velocity vact that is clearly lower than the speed limit, which is thus slower than the vehicle has to travel to avoid exceeding the speed limit In other words, the vehicle will have a longer travel time for a predetermined stretch than it would have needed to have, as a lower velocity than necessary was maintained. This unnecessarily low velocity and the resulting longer travel time are experienced as annoying by the driver himself, and by other drivers on the road. The risk is consequently great that the driver will inactivate the cruise control in the vehicle in order to avoid this annoying situation.
The known cruise control thus results in a non-optimal velocity profile for the actual velocity vact of the vehicle, wherein said velocity is often either lower than it needs to be, which results in an unnecessarily prolonged travel time, or so high that the driver is at risk of incurring speeding fines. The risk of being fined causes the driver to occasionally brake on downhill stretches, which is inefficient from a fuel economics standpoint.
One object of the present invention is to provide a cruise control that results in an actual vehicle velocity vact that is as close to the speed limit as possible, while at the same time not exceeding said speed limit.
This object is achieved by the aforementioned method for adjusting the set points for regulating velocity according to the characterizing portion of claim 1. The object is also achieved by the aforementioned system for adjusting the set points for regulating velocity [according to claim] 15, and by the aforementioned computer program and computer program product.
According to the present invention, the value of a velocity set point vref and a braking set point vdhsc
The velocity set point vref and the braking set point vdhsc
This causes the velocity set point vref and the braking set point vdhsc
In other words, a common hysteresis is achieved by means of the present invention, which hysteresis automatically switches between two hysteresis values, with the difference corresponding to the offset voffset between the hysteresis values. A control of the set points is hereby achieved simply and with very little contribution to the complexity of the cruise control system, which control of the set points results in rapid and flexible cruise control close to speed limits.
Utilizing the present invention thus provides a set point hysteresis that enables adjustment toward and the maintaining of an actual vehicle velocity vact that is close to the speed limit without the vehicle having to maintain an unnecessarily low velocity on flat roads, and without the risk of incurring speeding fines and/or a driver license “demerit point” on downhill stretches. In other words, the set point hysteresis according to the invention results in the cruise control being carried out in a manner that feels intuitively correct to a driver of the vehicle. This is because the actual vehicle velocity vact that results from the cruise control when the invention is utilized can track speed limits extremely well, since a maximally high average actual vehicle velocity vact will be the result. Because the average actual vehicle velocity vact is maximized, the travel time for a road section or road on which the vehicle is traveling is minimized.
The desire of the driver to use the cruise control system, i.e. the cruise control and the downhill speed control, will be increased as a result. As the utilization of these systems increases as a result of greater understanding and acceptance of the systems, total fuel consumption will decrease as well, since these systems generally operate the vehicle more efficiently than the driver himself would have done by means of fully manual speed control.
According to one embodiment of the invention, the shift vshift between the end values/hysteresis values of the set points occurs via a ramping between the end values, which enables gentler and more comfortable regulation of the actual vehicle velocity vact.
The invention will be elucidated in greater detail below based on the accompanying figures, in which the same reference designations are used for the same components, and wherein:
A vehicle is affected by its own weight as it travels. This effect is especially pronounced on uphill and downhill stretches that are relatively steep. A steep uphill stretch refers here to a hill on which the vehicle will lose velocity due to its heavy train weight in relation to the engine performance of the vehicle. The vehicle will accelerate on a steep downhill stretch in a corresponding manner, due to its heavy train weight.
Because the downhill speed control velocity vdhsc is related to the set velocity vset by an offset velocity, vdhsc=vset+voffset, an undesirable profile is often obtained for the actual velocity of the vehicle vact, particularly on hilly roads. Said profile is undesirable because it often results in an unnecessarily low actual vehicle velocity vact on flat roads and/or an actual vehicle velocity vact that exceeds the speed limits on long downhill stretches.
An actual behavior for the vehicle is analyzed in a first step 101 of the method. As described below, such an actual behavior can comprise an actual velocity vact for the vehicle, the utilization of a driving torque from the engine system and/or the utilization of braking action by the downhill speed control.
An adjustment of the velocity set point vref is performed in a second step 102 of the method, which set point constitutes a set point for the cruise control, and of the braking set point vdhsc
The velocity set point vref is utilized in a third step 103 of the method as a set point in connection with the regulation of the cruise control, while the braking set point vdhsc
Through this adjustment of the set points for the cruise control, i.e. of the velocity set point vref, and for the downhill speed control, i.e. of the braking set point vdhsc
According to one embodiment of the present invention, the adjustment of both the velocity set point vref and the braking set point vdhsc
The curve 202 illustrates whether and when the cruise control will demand torque from the engine system in the vehicle. This is illustrated here schematically for the curve 202 with a low value (zero) when no torque is demanded and a high value (one) when torque is demanded from the engine system.
The curve 203 schematically illustrates a third t3 hysteresis timer, which will be described in greater detail below.
The curve 204 illustrates whether and when the downhill speed control will demand braking torque from the brake system in the vehicle. This is illustrated here schematically for the curve 204 with a low value (zero) when no torque is demanded and a high value (one) when braking torque is demanded.
The curve 205 schematically illustrates a fourth t4 hysteresis timer, which will be described in greater detail below.
The curve 206 schematically illustrates a first t1 hysteresis timer, which will be described in greater detail below.
The curve 207 schematically illustrates a second t2 hysteresis timer, which will be described in greater detail below.
The curve vref shows the velocity set point vref that is used to control the engine system in the vehicle. The curve vdhsc
According to one embodiment of the invention, the adjustment of the velocity set point vref and the braking set point vdhsc
The ways in which the shift of the velocity set point vref and the braking set point vdhsc
According to one embodiment of the present invention, which is illustrated schematically in
According to this embodiment of the invention, both the velocity set point vref and braking set point vdhsc
Both the velocity set point vref and the braking set point vdhsc
According to one embodiment of the invention, both the velocity set point vref and the braking set point vdhsc
As
The adjustments between the two extreme positions for both the velocity set point vref and the braking set point vdhsc
An adjustment of the velocity set point vref is hereby achieved between one end value corresponding to the set velocity vset, vref=vset, and one end value corresponding to the set velocity vset minus the offset voffset, vref=vset−voffset. The braking set point vdhsc
As shown in
According to one embodiment of the present invention, the adjustment of the velocity set point vref and the braking set point vdhsc
Here both the velocity set point vref and the braking set point vdhsc
According to one embodiment of the present invention, the adjustment of the velocity set point vref and the braking set point vdhsc
The adjustments between the two extreme positions for both the velocity set point vref and the braking set point vdhsc ref can, according to one embodiment of the invention, be performed in alternating fashion, so that the velocity set point vref and the braking set point vdhsc
Here again the adjustments result in a common hysteresis for the velocity set point vref and the braking set point vdhsc
An adjustment of the velocity set point vref is hereby obtained between one end value corresponding to the set velocity vset, vref=vset and one end value corresponding to the set velocity vset minus the offset voffset, vref=vset−voffset. The braking set point vdhsc
In the first state S1, the first t1 and/or the third t3 hysteresis timer is/are activated. As described above, the first hysteresis timer t1 begins to increment in the first state S1 when the actual velocity vact of the vehicle exceeds the set velocity vset. If the actual velocity vact falls below the set velocity vset again, the first hysteresis timer ta is zeroed. The third hysteresis timer t3 will increment correspondingly in the first state S1 if no driving torque is demanded from the engine system. If a driving torque is demanded, the third hysteresis timer t3 is zeroed again.
If the first hysteresis timer ta reaches the first predetermined time period T1, or if the third hysteresis timer t3 reaches the third predetermined time period T3, then the set points i.e. the velocity set point vref and the braking set point vdhsc
The second t2 and/or the fourth t4 hysteresis timer is/are activated in the second state S2. The second hysteresis timer t2 begins to increment in the second state S2 when the actual velocity vact of the vehicle falls below the set velocity vset. If the actual velocity vact exceeds the set velocity vset again, the second hysteresis timer t2 is zeroed. The fourth hysteresis timer t4 will be correspondingly incremented in the second state S2 if no braking action is utilized. If the braking action is utilized, the fourth hysteresis timer t4 is zeroed again.
If the second hysteresis timer t2 reaches the second predetermined time period T2, or if the fourth hysteresis timer t4 reaches the fourth predetermined time period T4, then the set points, i.e. the velocity set point vref and the braking set point vdhsc
According to one embodiment of the present invention, the adjustment of the velocity set point vref and the braking set point vdhsc
According to one embodiment, a determination is made as to whether the downhill stretch has a length exceeding the predetermined length L based on map data and positioning data such as GPS (Global Positioning System). Map data with topographical information are currently available, and can be used together with a determined position of the vehicle to determine the length of a downhill stretch in front of the vehicle. Other information, such as radar information in combination with information related to the road inclination can also be used to determine whether the length of the downhill section exceeds the predetermined length L. The predetermined length L can be set so that no engine torque will be demanded from the engine system, for example, for a time corresponding to the third predetermined time period T3. The adjustment of the set points based on the actual behavior of the vehicle can thereby be carried out by analyzing whether the length of the downhill stretch exceeds the predetermined length L.
According to one aspect of the present invention, a system for regulating the velocity of a vehicle is provided.
Said system comprises a cruise control, which regulates an engine system with a velocity set point vref, wherein the regulation is based on a selected set velocity vset chosen by, for instance, a driver. The system further comprises a downhill speed control, which regulates a brake system in the vehicle with a braking set point vdhsc
The system further comprises an adjusting element, which is arranged so as to adjust the velocity set point vref and the braking set point vdhsc
One skilled in the art will perceive that a method for adjusting the set points according to the present invention could also be implemented in a computer program which, when it is executed in a computer, results in the computer carrying out the method. Said computer program normally consists of a computer program product 403 stored on a digital storage medium, wherein the computer program is contained in the computer-readable medium of the computer program product. Said computer-readable medium consists of a suitable memory, such as: ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically Erasable PROM), a hard disk unit, etc.
The control unit 400 is further provided with devices 411, 412, 413, 414 for respectively receiving and transmitting input and output signals. Said input and output signals can have waveforms, pulses or other attributes that can be detected by the devices 411, 413 for receiving input signals as information, and can be converted into signals that can be processed by the calculating unit 401. Said signals can then be furnished to the calculating unit 401. The devices 412, 414 for transmitting output signals are arranged so as to convert signals received from the calculating unit 401 to produce output signals by, e.g., modulating the signals, which can be transferred to other parts of the system for adjusting the set points and/or for use in controlling actuators in the system.
Each and every one of the connections to the devices for respectively receiving and transmitting input and output signals can consist of one or more of a cable, a data bus, such as a CAN bus (Controller Area Network bus), a MOST bus (Media Orientated Systems Transport bus), or any other bus configuration, or of a wireless connection.
One skilled in the art will perceive that the aforesaid computer can consist of the calculating unit 401, and that the aforesaid memory can consist of the memory unit 402.
One skilled in the art will also perceive that the foregoing system can be modified according to the various embodiments of the method according to the invention. Furthermore, the invention pertains to a motor vehicle, such as a goods vehicle or a bus, comprising at least one system for adjusting the set points according to the invention.
The present invention is not limited to the embodiments of the invention described above, but pertains to and includes all embodiments within the protective scope of the accompanying independent claims.
Claims
1. A method for adjusting set points for regulating velocity of a vehicle, wherein the velocity regulation uses at least:
- a cruise control, which is configured and operable to control an engine system of the vehicle by setting a velocity set point vref based on a selected set velocity vset; and
- a downhill speed control, which is configured and operable to control a brake system of the vehicle with a braking set point vdhsc—ref based on a downhill speed control velocity vdhsc of the vehicle, wherein the downhill speed control velocity vdhsc is related to the set velocity vset by an offset voffset;
- the method comprising: adjusting the velocity set point vref and the braking set point vdhsc—ref by at least one shift vshift, which has a value corresponding to the offset voffset, vshift=voffset; wherein the adjusting is performed based on an actual behavior of the vehicle.
2. A method according to claim 1, wherein the adjusting by the at least one shift vshift constitutes a common hysteresis for the velocity set point vref and for the braking set point vdhsc—ref.
3. A method according to claim 1, wherein
- the actual behavior comprises an actual velocity vact for the vehicle; and
- the adjusting adjusts the velocity set point vref and the braking set point vdhsc—ref downward by the offset voffset if the actual velocity vact exceeds the set velocity vset for a first predetermined time period T1.
4. A method according to claim 1, wherein
- the actual behavior comprises an actual velocity vact for the vehicle; and
- the adjusting adjusts the velocity set point vref and the braking set point vdhsc—ref upward by the offset voffset if the actual velocity vact is below the set velocity vset for a second predetermined time period T2.
5. A method according to claim 3, wherein the adjusting alternatingly adjusts the velocity set point vref and the braking set point vdhsc—ref downward or upward by the offset voffset as follows:
- downward if the actual velocity vact exceeds the set velocity vset for a first predetermined time period T1, and
- upward if the actual velocity vact is below the set velocity vset for a second predetermined time period T2.
6. A method according to claim 1, wherein
- the actual behavior comprises using a driving torque from an engine system in the vehicle; and
- the adjusting adjusts the velocity set point vref and the braking set point vdhsc—ref downward by the offset voffset if the vehicle is driven without the driving torque for a third predetermined time period T3.
7. A method according to claim 1, wherein
- the actual behavior comprises using a braking action from a downhill speed control; and
- the adjusting adjusts the velocity set point vref and the braking set point vdhsc—ref upward by the offset voffset if the vehicle is driven without the braking action for a fourth predetermined time period T4.
8. A method according to claim 6, wherein the adjusting alternatingly adjusts the velocity set point vref and the braking set point vdhsc—ref downward or upward by the offset voffset as follows:
- downward if the vehicle is driven without the driving torque for a third predetermined time period T3; and
- upward if the vehicle is driven without the braking action for a fourth predetermined time period T4.
9. A method according to claim 1, wherein the adjusting adjusts the velocity set point vref and the braking set point vdhsc—ref downward by offset voffset if the vehicle is on a downhill stretch that has at least a predetermined length L.
10. A method according to claim 1, wherein the adjusting results in a hysteresis for the velocity set point vref and the braking set point vdhsc—ref, which automatically alternates between two hysteresis values, wherein a difference between the two hysteresis values is defined by the offset voffset.
11. A method according to claim 1, wherein the at least one shift vshift is applied gradually so that the velocity set point vref and the braking set point vdhsc—ref are ramped from a first to a second respective value.
12. A method according to claim 1, wherein the set velocity vset is related to a speed limit for a road section on the said vehicle is located.
13. (canceled)
14. A computer program product comprising a non-transitory computer-readable medium and a computer program comprising program code contained in the computer-readable medium, and which, when the program code is executed in a computer, causes the computer to cause performance of the method of claim 1.
15. A system for regulating the velocity of a vehicle comprising at least:
- a cruise control, which regulates an engine system with a velocity set point vref based on a selected set velocity vset;
- a downhill speed control, which regulates a brake system with a braking set point vdhsc—ref based on a downhill speed control velocity vdhsc, wherein the downhill speed control velocity vdhsc is related to the set velocity vset by an offset voffset; and
- an adjusting element, configured and arranged to adjust the velocity set point vref and the braking set point vdhsc—ref by at least one shift vshift, which has a value corresponding to the voffset, vshift=voffset, wherein the adjusting element is arranged so as to perform the adjusting based on an actual behavior of the vehicle.
16. A method according to claim 4, wherein the adjusting alternatingly adjusts the velocity set point vref and the braking set point vdhsc—ref downward or upward by the offset voffset as follows:
- downward if the actual velocity vact exceeds the set velocity vset for a first predetermined time period T1, and
- upward if the actual velocity vact is below the set velocity vset for a second predetermined time period T2.
Type: Application
Filed: Mar 26, 2013
Publication Date: Nov 19, 2015
Inventor: Ulf CARLSSON (Södertälje)
Application Number: 14/389,893